In facial recognition for biometric verification, the face of a person is used for verifying identity and authorizing access. Face information extracted from those images is compared to enrollment face information. If the captured face matches the enrollment data then the verification succeeds and the user is granted access.
However, such verification technique can be easily spoofed. One could be granted access simply by presenting a picture of an authorized person. One possible countermeasure is a liveness detector which attempts to determine whether the identified person presented is indeed alive.